Annual report pursuant to Section 13 and 15(d)

EMPLOYEE BENEFITS AND STOCK BASED COMPENSATION (Narrative) (Details)

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EMPLOYEE BENEFITS AND STOCK BASED COMPENSATION (Narrative) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Apr. 20, 2015
Defined Benefit Plan Disclosure [Line Items]        
Deferred compensation plans obligation to Board of Directors $ 15,800,000 $ 15,700,000    
Maximum term of stock options 10 years      
Stock options granted 0      
Vesting period of stock awards 5 years      
Number of stock option awards exercised 46,278 56,619 72,743  
Intrinsic value of stock options exercised $ 555,000 $ 684,000 $ 1,900,000  
Fair value of stock options exercised 1,600,000 2,100,000 2,800,000  
Cash received from the exercise of stock options 1,000,000.0 1,400,000 983,000  
Tax benefit from exercise of equity-based awards $ 112,000 127,000 390,000  
Restricted stock vesting percentage 33.33%      
Intrinsic value of stock options outstanding $ 798,340 $ 2,300,000 $ 656,000  
Unamortized compensation costs $ 10,990,000      
Stock and Incentive Plan        
Defined Benefit Plan Disclosure [Line Items]        
Number of shares authorized to be issued, maximum 2,500,000      
Number of shares available for future issuance 666,858      
2011 Plan        
Defined Benefit Plan Disclosure [Line Items]        
Number of shares authorized to be issued, maximum       1,000,000
Restricted Stock        
Defined Benefit Plan Disclosure [Line Items]        
Restricted stock units, vesting terms RSAs vest one-third on each of the first, second and third anniversaries from the date of the grant      
Restricted Stock and Performance Stock Awards | Minimum        
Defined Benefit Plan Disclosure [Line Items]        
Vesting period of stock awards 3 years      
Restricted Stock and Performance Stock Awards | Maximum        
Defined Benefit Plan Disclosure [Line Items]        
Vesting period of stock awards 4 years      
1% through 3%        
Defined Benefit Plan Disclosure [Line Items]        
Percentage of employer's match for 401(k) plan 100.00%      
1% through 3% | Minimum        
Defined Benefit Plan Disclosure [Line Items]        
Percentage of employee's gross pay for 401(k) plan 1.00%      
1% through 3% | Maximum        
Defined Benefit Plan Disclosure [Line Items]        
Percentage of employee's gross pay for 401(k) plan 3.00%      
4% through 5%        
Defined Benefit Plan Disclosure [Line Items]        
Percentage of employer's match for 401(k) plan 50.00%      
4% through 5% | Minimum        
Defined Benefit Plan Disclosure [Line Items]        
Percentage of employee's gross pay for 401(k) plan 4.00%      
4% through 5% | Maximum        
Defined Benefit Plan Disclosure [Line Items]        
Percentage of employee's gross pay for 401(k) plan 5.00%      
Access National Bank        
Defined Benefit Plan Disclosure [Line Items]        
Maximum term of stock options   5 years    
Vesting period of stock awards   4 years